I frequent /r/pygame and lurk on /r/GameDev. Honestly I don't much like the Reddit format and the upvoting and downvoting ends up having a more negative than positive effect in a lot of cases in my opinion. It is much too easy to game the system by having a PR crew backing you, and it just doesn't generally feel like a forum. I do find interesting articles through it though, and if I ever get to the point where I'd be able to release a commercial project it is an essential place for promoting.